Multi-position tilt-limiting mechanism

ABSTRACT

A chair back upright rotates about a pivot axis with respect to a chair seat plate and has a protrusion on the bottom portion thereof. When the occupant of a chair reclines, the protrusion on the back upright and the stop make contact with each other. The contact stops the rotation of the back upright. The lever handle, fixedly attached to the stop, can be rotated thereby providing more or less rotation of the back upright before contacting the protrusion and the stop occurs.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates in general to a chair in which the back upright portion is pivotable relative to the seat and, in particular, to a mechanism that provides a multi-position tilt limit adjustment for the back upright.

[0003] 2. Description of Related Art Including Information Disclosed Under 37 C.F.R. §§1.97 and 1.98

[0004] There are many chairs, particularly for use in offices, but not limited thereto, that have a back rest that is pivotable relative to the chair seat or the chair base to allow the user to select an angle at which the seat is most comfortable for him or her. One such tilt-limiting mechanism is discussed in U.S. Pat. No. 6,102,477 that has a complex mechanism for making the adjustment to the tilt angle of the back rest.

[0005] Further, U.S. Pat. No. 4,408,800 discloses an office chair that has a pneumatic cylinder operated by a cam that can adjust the attitude of the back rest over a continuous range about a pivot. U.S. Pat. No. 4,509,793 discloses a chair in which the inclination of the back rest portion and the seat portion can be varied.

[0006] Finally, in German Patent No. 2,218,941, an adjustable chair back is disclosed in which a back rest holding bracket has an extension that projects toward the center under the seat. The back rest angle is determined by locking the end of the extension against a lock plate in the desired position. The extension has a plate with a series of indentations formed in an essentially arcuate manner that engages a spring-loaded arm to hold the back rest in one of a plurality of positions.

[0007] Each of these patented devices is complex and complicated. It would be desirable to have a simple, tilt-limiting mechanism that enables multi-tilt positions of the seat back to be achieved.

SUMMARY OF THE INVENTION

[0008] The present invention achieves the desired goal of providing a simple multi-tilt limiting mechanism for a chair back upright with the use of an engaging member affixed to the lower end of the back upright and a stop rotatatively affixed to the bottom side of the seat plate. The stop has an outer edge with a changing radius for interacting with the engaging member on the chair back such that rotation of the stop enables the back upright to be tilted forward and backward with respect to the seat plate. A lever handle is coupled to the stop to enable the user to rotate this stop and select the tilt position of the back upright from a minimum tilt to a maximum tilt.

[0009] In the preferred embodiment, a stepped surface forms the outer edge of the stop for interfacing with the engaging member on the lower end of the back upright. The engaging member may be in the form of a protrusion. The stepped surface has multiple steps such that each step, when engaging the protrusion, enables the back upright to assume the selected tilt position.

[0010] The tilt limiting mechanism further comprises a locking means for holding a stop in a selected rotatable position to provide a fixed tilt position of the back upright. To provide the locking means, a series of indexing detents is formed in the top side of the rotatable stop with each detent representing a selected upright tilt position. A biased plunger is mounted between the bottom side of the seat plate and the rotatable stop such that the plunger is engagable with any selected indexing indent to hold the stop in a selected rotated position. The indexing detents have a concave shape and are adjacent to each other and the plunger is in the form of a spring-loaded plunger so as to enable it to freely move from one concave detent to another while compressing the spring. When the plunger is in any selected detent, the spring urging the plunger in that the detent causes the stop to hold the seat back upright tilt in the selected position.

[0011] Thus, it is the object of the present invention to provide a multi-position tilt-limiting mechanism for a chair back upright.

[0012] It is another object of the present invention to provide a protrusion affixed to the lower end of the back upright for engaging a stop rotatively affixed to the bottom side of the chair seat plate.

[0013] It is another object of the present invention to provide an outer edge on this stop having a changing radius for engaging the protrusion so that rotation of the stop enables the back upright to be tilted forward and backward with respect to the seat plate.

[0014] It is another object of the present invention to provide a lever handle coupled to the stop to enable a user to rotate the stop and select a tilted position of the back upright from a minimum tilt to a maximum tilt.

[0015] It is yet another object of the present invention to provide a stepped surface forming the outer edge of the stop for engaging a protrusion at the lower end of the seat back upright, the stepped surface having multiple steps such that each step position for engaging the protrusion enables the back upright to assume a given tilted position.

[0016] It is also another object of the present invention to form the locking means with a series of indexing indents on the top side of the rotatable stop wherein each detent represents a selected back upright tilt position. A spring-loaded plunger is mounted between the bottom side of the seat plate and the rotatable stop such that the plunger engages any selected one of the detents to hold the stop in a selected rotated position to limit the back upright position to the selected tilt position.

[0017] Thus, the invention relates to a multi-position tilt-limiting mechanism for a chair back upright, the back upright having an upper end and a lower end, the chair having a seat plate with a top side and a bottom side and the back upright being tiltable with respect to the seat plate. The tilt-limiting mechanism comprises a protrusion affixed to the lower end of the back upright, a rotatable stop being affixed to the bottom side of the seat plate and having an outer edge with a changing radius for engaging a protrusion such that rotation of the stop enables the back upright to be tilted forward and backward with respect to the seat plate. A lever handle is coupled to the Stop to enable a user to rotate the stop and select a tilt position from a minimum tilt to a maximum tilt.

[0018] The present invention is part of a complete new claim construction as disclosed and claimed in U.S. application Ser. No. ______ (Attorney Docket No. 785135), entitled “Ergonomic Chair,” filed on even date herewith, the complete disclosure of which is incorporated by reference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and other objects of the present invention will be more fully described, and when taken in conjunction with the following detailed description of the drawings wherein like numerals represent like elements and wherein:

[0020]FIG. 1 is a perspective view of the bottom of the seat plate and illustrates the stop and its control mechanism in exploded form;

[0021]FIG. 2 is a top view of the stop illustrating the stepped outer edge representing a changing radius and also the indexing detents of the spring plunger;

[0022]FIG. 3 is a perspective view of the back upright frame illustrating the engaging member at the bottom thereof; and

[0023]FIG. 4 is a bottom view of the seat plate and back upright illustrating the simplicity of the stop having the changing outer radius to engage the back upright engaging member and thus set the tilt limit of the chair back upright.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0024]FIG. 1 is a bottom perspective view of the chair seat plate illustrating an exploded view of the stop, and its method of attachment to the bottom of the seat plate.

[0025] As can be seen in FIG. 1, seat plate 10 has a mount 12 on the bottom side thereof to which stop plate 14 and lever handle 16 can be attached by a shoulder bolt 18 that is threadedly inserted into mounting bracket 12 through orifice 40. The lever handle could be attached to the stop plate from either side of the chair.

[0026] It will be noted that stop 14 has an outer edge 20 with a changing radius for interacting with engaging member 28 on the lower portion of the chair back upright as will be seen more clearly in FIG. 3. In the preferred embodiment, the member 28 is in the form of a protrusion The outer edge of stop 14 has specific steps 22, 24 and 26, as can be best seen in FIG. 2, each having a different distance from axis 40 with respect to the other. A locking means 30, in the form of a spring-biased plunger, is mounted in a bracket 32 on the base of seat plate 10 and engages detents in the upper portion of stop 14. The detents are shown in detail in FIG. 2. It will be noted that the outer edge 20 of stop plate 14 could be a cam having an outer edge with a continuously changing radius. The number of detents (34, 36, 38) would determine the number of chair back tilt positions.

[0027] As can be seen in FIG. 2, there are three indexing detents 34, 36 and 38 (for example only) in the top surface of stop 14. It will be noted that these indexing detents are of concave shape and are adjacent each other. Since the spring-loaded plunger is in the form of a spring-loaded ball, as can be best seen in FIG. 1, the plunger is enabled to freely move from one concave detent to another by compressing the spring and rotating the stop member 14 to prevent the plunger to be pointed in any selected detent and by releasing the plunger to cause the stop to hold the back upright in a selected tilt position.

[0028] The protrusion 28 can best be seen in FIG. 3. It is on the lower portion of the back upright 42. The back upright 42 rotates about pivot axis 44. Since the protrusion 28 is below the pivot axis, as the back upright 42 pivots about axis 42, the protrusion 28 moves inwardly towards the seat plate stop and backwardly away from the seat plate stop thus allowing adjustment of the tilt mechanism by moving handle 16.

[0029]FIG. 4 is a bottom view of the seat plate 10 illustrating the stop or stop plate 14, the lever handle 16 and the stepped surface 22, 24 and 26 forming the outer edge of the stop 14 for engaging the protrusion 28 to change the tilt position of the back upright 42.

[0030] As can be clearly seen in FIG. 4, when the handle 16, fixedly attached to stop 14, is moved on a horizontal plane, stop plate 14 rotates about axis 40, thus placing the various steps 22, 24 and 26 on the outer edge thereof in selective engagement with the protrusion 28 on the lower portion of back upright 42 that pivots about axis 44.

[0031] As stated earlier, it will be apparent to one skilled in the art that the outer edge of stop 14 could be in a shape of a cam surface that has a continuously changing radius with respect to axis 40 to cause different stop positions for the back upright 42 as the stop is rotated. In such case, the detents 34, 36 and 38 in the top of stop plate 14 could be any number desired to achieve a desired range of minimum and maximum tilt of the back upright.

[0032] Thus there has been disclosed a novel and very simple tilt-limiting mechanism for the back upright of a chair simply by moving a stop 14 having an outer edge of changing radius for engaging a protrusion on the lower end of the chair back upright so that in a particular position of the stop, a particular tilt position of the back upright can be selected from a minimum tilt to a maximum tilt.

[0033] It should also be noted that although the stop 14 is illustrated as rotating in a horizontal plane about axis 40. It would be apparent to one skilled in the art that the pivot point 40 can be placed in a horizontal plane and the stop 14 rotated in a vertical plane about pivot point 40 and the same result could be achieved.

[0034] While the present invention has been described as in connection with a preferred embodiment thereof, it will be apparent to those skilled in the art that many changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is intended by the appended claims to cover all such changes and modifications encompassed by the spirit and scope of the appended claims. 

What is claimed is:
 1. A multi-position tilt-limiting mechanism for a chair having a back upright, said back upright having an upper and a lower end, said chair having a seat plate with a top side and a bottom side, and said back upright being tiltable with respect to said seat plate, the tilt-limiting mechanism comprising: an engaging member affixed to the lower end of said back upright; a stop member rotatably affixed to said seat plate and having an outer edge of different dimensions for interfacing with said engaging member such that rotation of said stop enables said back upright to be tilted forward and backward with respect to said seat plate; and an operating member coupled to said stop to enable a user to rotate said stop and select the tilt position of said back upright from a minimum tilt to a maximum tilt.
 2. The tilt-limiting mechanism of claim 1 further comprising: a stepped surface forming the outer edge of said stop for engaging said protrusion on the lower end of said back upright; and said stepped surface having multiple steps such that each step, when engaging said protrusion, enables of said back upright to assume a different given tilted position.
 3. The tilt-limiting mechanism of claim 1 further comprising: locking means for holding said stop in a selected rotatable position to provide a fixed tilt position of said back upright.
 4. The tilt-limiting mechanism of claim 3 wherein said locking means comprises: a top side and a bottom side on said rotatable stop, said top side facing said bottom side of said seat plate; a series of indexing detents in said top side of said rotatable stop, each detent representing a selected back upright tilt position; and a biased plunger mounted between said bottom side of said seat plate and said detents such that said plunger engages any selected one of said detents to hold said stop in a selected rotated position, thereby limiting said back upright position to said selected tilt position.
 5. The tilt-limiting mechanism of claim 4 wherein: said indexing detents are of concave shape and are adjacent to each other; and said plunger is in a form of a spring-loaded ball so as to enable said ball to freely move from one concave detent to another by compressing said spring, said spring urging said plunger in any selected detent to cause said stop to hold said back upright in a selected tilt position. 